Variable Magnetic Field Effect on Non-Newtonian Nanofluid Convective Flow in a Channel Containing Heated Permeable Blocks

Oscillating non-uniform magnetic field’s influence on unsteady forced convection of a non-Newtonian (EG-water/Fe3O4) nanofluid within a channel containing heated permeable blocks is numerically explored. The variable magnetic field is produced by magnetic sources positioned outside the system in the center of the blocks. The extended Darcy–Brinkman–Forchheimer model modified for power-law non-Newtonian fluids is used to describe the nanofluid flow. The finite-volume technique and the SIMPLE algorithm are employed to solve the physical problem’s equations and their boundary conditions. Some parameters’ effects are examined, including Strouhal St, Hartmann Ha, Darcy Da, Reynolds Re numbers, and behavior index n. The results reveal that the flow structure disturbances are more significant in the magnetic sources’ region, the first quarter of a cycle, and with the growth of Ha. The magnetic field’s ability to improve heat transfer rises as Ha, Da, and Re increase and n decrease. The shear-thinning fluids are more advantageous to heat transfer enhancement for Ha > 15, Da ≤ 10–2, and Re ≤ 200. The maximum values of ηHa=0 are 85%, 126%, and 58% at Ha = 50, Da = 10–4, and Re = 100, respectively. The magnetic field oscillatory aspect is thermally beneficial, whatever Ha, Da, Re, and n values are. The shear-thinning-nanofluids respond the best to the oscillation for all Hartmann and Darcy numbers, whereas they are the least reactive for Reynolds numbers between 150 and 700. The maximum values of ηSt=0 are 3.5%, 10%, and 5.4% at Ha = 15, Da = 10–5, and Re = 1000, respectively.